Retrofocus type objective lens system

Claim 2

A retrofocus objective lens system comprising a negative meniscus front first lens having a concave rear face, a biconvex second lens, a biconcave third lens, a positive meniscus fourth lens with a convex rear face, and a positive fifth lens, said lens system satisfying the following conditions: 1.6 (d.sub.5 + d.sub.6 + d.sub.7 + d.sub.8 + d.sub.9)> d.sub.4 > d.sub.5 + d.sub.6 + d.sub.7 + d.sub.8 + d.sub.9 0.7d.sub.4 < d.sub.3 < 1.3d.sub.4 ##EQU3##

Claim 3

wherein r j is the radius of curvature of the jth lens face successively designated from the front lens face, and d j is the axial distance between the jth and the j+1 lens faces of the lens system.

Claim 4

wherein r j is the radius of curvature of the jth lens face successively designated from the front lens face, and d j is the axial distance between the jth and the j+1 lens faces of the lens system.

Claim 5

A retrofocus type objective lens as set forth in claim 1, wherein the arrangement and construction of the five lenses are as follows:f=1.0 1:2.8 field angle 2ω=64° backfocus s'=1.06radius of length on refractive Abbe'scurvature axis index number______________________________________r1 = 2.3437r2 = 0.4709 d1 = 0.0441 N1 = 1.5714 v1 = 53.0r3 = 0.6206 d2 = 0.3538r4 =-1.8643 d3 = 0.28 N2 = 1.6583 v2 = 58.5r5 =-0.4012 d4 = 0.3182r6 = 2.3930 d5 = 0.0379 N3 = 1.6889 v3 = 31.2r7 =-1.4595 d6 = 0.0283r8 =-0.4496 d7 = 0.067 N4 = 1.7200 v4 = 50.3r9 = 2.4019 d8 = 0.0029r10=-1.1931 d9 = 0.068 N5 = 1.6204 v5 = 60.3______________________________________ wherein Vi is the Abbe's number of the ith lens.

Claim 6

A retrofocus type objective lens system set forth in claim 1, wherein the arrangement and construction of the five lenses are as follows. f=1.0 1:2.8 field angle 2ω=64° backfocus s'=1.06 radius of length refractive Abbe's curvature on axis index number ______________________________________ r1= 2.5414 r2= 0.4915 d1 = 0.0469 N1 = 1.5725 v1 = 57.5 r3 = 0.6600 d2 = 0.3284 r4=-1.8698 d3 = 0.3345 N2 = 1.6968 v2 = 55.6 r5=-0.4287 d4 = 0.2722 r6=2.1911 d5 = 0.0428 N3 = 1.7006 v3 = 30.1 r7=-1.9373 d6 = 0.0376 r8=-0.4795 d7 = 0.067 N4 = 1.7495 v4 = 50.1 r9=4.3712 d8 = 0.0029 r10=-1.1652 d9 = 0.068 N5 = 1.6214 v5 = 61.3 ______________________________________ Wherein Vi is the Abbe's number of the ith lens.